System Control And Data Acquisition or “SCADA” systems are routinely used in processing facilities to monitor and control the operation of processing equipment in the facilities. Monitoring devices in a conventional SCADA system typically monitor and collect information associated with different characteristics of a processing facility. The collected information is then made available to control devices, which use the information to determine how to control processing equipment in the facility.
A conventional monitoring device in a SCADA system may be polled to gather information collected by that device, and/or the monitoring device may report its collected information upon the occurrence of a specified event, or it may provide information on a continuous or periodic basis. If being polled, the monitoring device typically stores its information in registers that lie dormant until the information is retrieved by a control device. When an emergency or other “alarm” condition occurs, the monitoring device typically sends its data to a control device immediately and does not wait to be polled.
In a conventional SCADA system, monitoring devices typically represent devices that are physically wired to control devices in the SCADA system. Also, all or most of the processing in a conventional SCADA system is centralized and is performed by the control devices in the SCADA system, although some localized functions may be performed solely by devices such as programmable logic controllers (PLCs) with or without SCADA involvement.